Agreed, it should drop immediately, and I can almost tell you for sure what happened...as it's the only thing I can think of.

when reinstalling the pad into the upper part of the housing, you must make sure that the spring is seated in its little "holder" correctly. The problem is, the metal-metal contact point for the spring also has one of these divots. I'd almost bet that the spring is not connected properly at one of these two points, and you DO NOT want to just wait for it to pop in....because ONE side might decide to pop in during a hard corner....yeah not fun.

The lower metal housing has a habit i've noticed of getting dirt/mud in there.....take the springs out, clean out that carrier, make sure everything is flush, tight, and right, then put them back on. Also, I know everyone else has said it, but check to make sure that you don't have them switched front-to-back, as this WOULD still lower the rear, but would ALSO raise the front. As far as bump stops go it's a POSSIBILITY, but I never trimmed the bump stops on the N/A (the roads never warranted it) and my front still dropped the prescribed amount.

Hope this helps.